Field of the Invention
The present invention relates to an ophthalmologic imaging apparatus such as a fundus camera and an ophthalmologic imaging method used for a physical examination in a group checkup or a general checkup, and to a program therefore.
Description of the Related Art
Conventionally, a fundus examination is performed in a group checkup such as a resident checkup or a company checkup. Usually in fundus imaging in the group checkup, non-mydriatic imaging is performed, which does not need mydriatics. In the non-mydriatic imaging, an examination room is darkened, or a simple darkroom is used so that the eye to be inspected is shielded from indoor light, and thus natural mydriasis of the eye to be inspected is urged for imaging.
An ophthalmologic imaging apparatus that performs non-mydriatic fundus imaging includes an observation light source in an infrared wavelength range that usually does not cause miosis, and a visible imaging light source. In the fundus imaging, the observation light source is used for illuminating the fundus to perform positioning and focusing of the imaging apparatus. After that, an image is taken of the fundus illuminated by the imaging light source.
As to focusing, there is known a fundus camera of Japanese Patent Application Laid-Open No. 2011-50531 in which automatic focusing is performed on a specific section of the fundus of the eye to be inspected. In the fundus camera described in Japanese Patent Application Laid-Open No. 2011-50531, a focus evaluation value is calculated based on a focus state detection unit that detects contrast of a specific section in the fundus of the eye to be inspected, and the automatic focusing is performed on a focus position that is a position at which the focus evaluation value becomes maximum. In addition, the fundus camera of Japanese Patent Application Laid-Open No. 2011-50531 includes an illumination light amount control unit that adjusts the illumination light amount of the light source for observation as a technique for realizing more accurate automatic focus. The illumination light amount control unit controls the illumination light amount based on an output of the focus state detection unit.
When detecting contrast of the fundus of the eye to be inspected, because brightness of the fundus is different for each eye to be inspected, and because the light source for observation also has an individual variation, brightness of the fundus in observation has a variation. This variation also affects detection of a contrast value, and hence stable focus detection cannot be performed. Therefore, in order to perform stable focus detection, it is necessary to detect brightness of the fundus in advance and to adjust the illumination light amount in accordance with the brightness. In order to adjust the illumination light amount, it is necessary to detect the illumination light amount.
The fundus camera disclosed in Japanese Patent Application Laid-Open No. 2011-50531 uses a focus state detection unit so as to output the focus evaluation value based on the contrast calculated from a luminance value of each pixel in the fundus image, and detects a local maximum value of the focus evaluation value so as to perform focus evaluation. In addition, because the focus evaluation value refers to the luminance value of the fundus image, it is possible to detect whether or not the luminance value is saturated at the same time as the focus evaluation. If the luminance value is saturated, the illumination light amount is adjusted.
However, after starting the focus evaluation, if the illumination light amount is adjusted so as to change the observation condition for the fundus, the contrast value of the fundus image also changes. Therefore, it is necessary to search for the local maximum value of the focus evaluation value again. In this case, it takes time to obtain an in-focus state, or extra amount of light illuminates the eye to be inspected, which increases a load on an examiner or a subject.